The present invention relates to cone-shaped holders for a machine tools, as well as to methods for modifying such holders.
Cone-shaped holders or fasteners for machine tools are previously known, for example, through U.S. Pat. No. 4,818,161, the disclosure of which is incorporated by reference herein. Such a holder 101, depicted in accompanying FIG. 1, comprises a cone-shaped base body 100 having an end surface of small diameter in which a bore 2 is formed, the bore 2 having an internal screw thread 3. The body 100 also includes a large diameter end into which a tool (e.g., an end mill) is to be mounted. An external annular flange 5 extends around that large-diameter end. The flange 5 has circumferentially extending external grooves 7 formed therein for enabling an automated tool holder changer (not shown) to carry the tool holder while automatically removing or inserting the tool holder relative to a spindle of a machine tool such as a milling machine. The flange 5 includes a pair of diametrically opposed recesses 9 (only one depicted in FIG. 1) which are adapted to receive a respective drive lug (not shown) rigidly mounted to the spindle in order to transmit rotary motion from the spindle to the holder.
This type of holder may be developed in accordance with different standards, such as DIN-standard or ISO-standard. Among the DIN-standard, for example, are DIN 2080 and DIN 69871 which relate to two different cones, that are extremely dimensionally close to each other. For example, said cones have the same cone angle. Nevertheless, these cones are not compatible with each other when it comes to handling of said cones during tool changing. In cones 101a made according to DIN 2080 (shown in FIG. 2) the diametrically opposed recesses 9xe2x80x2a, 9xe2x80x2b in the flange 5 have the same depth d1. On the other hand, in cones 101b made according to DIN 69871 (shown in FIG. 3) the corresponding recesses 9xe2x80x3a, 9xe2x80x3b have different depths d1, d2 in order to ensure that the holder can be mounted only in the proper orientation in the spindle. Cones according to DIN 2080 are substantially intended for manual tool changing while cones according to DIN 69871 are substantially intended for automatic tool changing.
Both DIN 2080 and DIN 69871 are provided in a metric variant and an inch variant regarding the internal thread of the recess at the small-diameter end of the cone.
There is also a cone designated ISO 297, which substantially corresponds to the cone DIN 2080. There is additionally a cone designated ISO 7388, which substantially corresponds to the cone DIN 69871.
Due to the fact that the holder 101 a has different depth characteristics for the recesses 9xe2x80x2a, 9xe2x80x2b, as compared to the depth characteristics for the recesses 9xe2x80x3a, 9xe2x80x3b of the holder 101b, it is necessary to manufacture different cone bodies to satisfy this difference. That need adds to the expense of manufacturing and the cost of inventorying a sufficient number of holders.
A primary object of the present invention is to provide a holder of this general type that can be easily modified, whereby the same cone-shaped base body can be used with at least two different DIN- or ISO-standards.
Another object of the present invention is that the cone-shaped base body can be modified into metric standard or inch standard regarding the internal thread of the recess at the end of smaller diameter.
Still another object of the present invention is that cones with integral cutting tools can be utilized in more machines.
The present invention relates to a holder for a machine tool. The holder includes a cone-shaped base body having a large-diameter end and a small-diameter end, the large-diameter end including an annular flange having first and second diametrically opposite recesses formed therein. Each of the recesses includes a bottom surface. The first and second recesses include identical distances from the respective bottom surfaces to an outer periphery of the flange. One of the recesses includes a hole. A depth-reducing element is securable in the hole such that an outer surface of the element is disposed between the bottom surface and the outer periphery, wherein an effective depth of the recess having the depth-reducing element is shorter than an effective depth of the other recess.
The invention also pertains to a method of modifying a cone-shaped tool holder which includes a small-diameter end and a large-diameter end. The large-diameter end includes a flange, the flange having diametrically opposed recesses formed therein. Each recess includes a bottom surface. The recesses have identical first distances from the respective bottom surfaces to an outer periphery of the flange. The method comprises the step of inserting a depth-reducing element into a hole formed in the bottom surface of one of the recesses, wherein a second distance from the flange outer periphery to an outer surface of the depth-reducing element is less than the first distance.